Answer:
D. The decline of the Ottoman Empire following Suleyman the Magnificent's reign
Step-by-step explanation:
The Safavid Empire was founded in 1501 by the Safavid Shahs, following the banning of Shi'a Islam in Ottoman territory. The declaration outlawing Shi'a Islam led to the fleeing of Shi'a soldiers who joined with and strengthen the Safavid Empire
The Ottoman Empire, from which the Shi'a soldiers joined to strengthen the Safavid, signed a formal peace agreement with the Safavids in 1555, and the Ottoman Empire began declining in 1571 following the Battle of Lepanto, after Suleyman the Magnificent's reign
Therefore, the Safavid Empire was able to become one of the world's most powerful Muslim states partly because of the decline of the Ottoman Empire